Research On Detection And Control Strategy Of Unified Power Quality Controller

As China enters the era of Industry 4.0,More and more complicated load,Equipment is also becoming more and more sensitive,This brings some power quality problems,Such as:three-phase imbalance?Harmonic pollution?Voltage distortion,etc.Leading users to higher and higher power quality requirements.Unified power quality controller(UPQC)it is a power device with comprehensive adjustment of power quality.Not only a flexible integration of the structure,but also a perfect coordination of functions.Many countries and scholars have increased theoretical and experimental research on UPQC.In this paper,the topological structure,detection method and control strategy of UPQC are deeply studied,a new topology is proposed and new detection methods and compensation strategies are designed.Firstly,the topology of UPQC is analyzed,formally improved the traditional topology MMC-UPQC.The connection of the traditional MMC-UPQC structure results in the zero-sequence voltage of the series terminal not being coupled to the feeder side,and the zero-sequence voltage cannot be compensated.In the new MMC-UPQC topology,two inverters are connected in parallel on the series side.According to the star connection method,the other end directly accesses the feeder,which solves the problem that the traditional topology cannot compensate for the zero sequence voltage,and when the common DC side is the same,the output current of the new topology is twice the output current of the conventional structure.If the serial inverter fails or does not work properly,the topology at this time is equivalent to the traditional structure,and can continue to work for a certain period of time to maintain voltage stability.Secondly,the detection method was studied.Introduced traditional detection methods such as instantaneous reactive power.Based on the analysis of the advantages of these detection methods,a new detection method is given.In the dq coordinates,the new method can detect not only voltage harmonics and voltage distortion components,but also harmonics and reactive currents.As long as the currentiis projected onto the normal of the voltage u,the biggest advantage of this algorithm is that it can detect multiple powers,wide range of use.Finally,the compensation control strategy is analyzed,the principle of control methods such as triangular carrier modulation method is introduced,mainly to analyze the minimum energy compensation method in detail.When studying this compensation strategy,get inspired in vector,analysis of its compensation strategy from apparent power.By analyzing the relationship between the injection angle and each vector,without affecting the amount of compensation,find an optimal injection angle,find the amplitude by controlling the injection angle of the voltage,find the maximum voltage to achieve the best compensation for UPQC.